(1) Field of the Invention
The present invention relates generally to rotary cutter heads for industrial wood working machines, more particularly, to improved cutting inserts for use in cutterheads for peripheral milling machines, including high speed planers and molders.
(2) Description of the Prior Art
Historically, rotary cutterheads used in industrial wood working machines, such as high speed planers, have been characterized by designs having straight, high speed steel knives clamped in the cutterhead body. More recently, stagger tooth arrangements for noise reduction and cutterheads with large numbers of knife rows for increased feed rates without increased RPM's have been introduced. The clamped-in-place solid knife design does not lend itself to the use of tool material other than high speed steel, because the replacement of knives is often tedious and costly. In addition to limitations on the types of cutting materials that can be used, there are also limitations on the ability to adjust the position of the cutting blades to meet different machining requirements.
U.S. Pat. No. 5,002,104 issued to John S. Stewart, the present inventor, the patent being incorporated herein by reference in its entirety, describes improved cutterheads with a sufficient number of knife rows to permit a staggered tooth arrangement for noise reduction or, alternatively, to provide an improved surface finish at higher feed rates without increasing cutterhead RPM, and provides for the generation of a variety of shapes when used with appropriately shaped individual cutting inserts.
The cutterhead described in the above patent is comprised of a cutterhead body and a plurality of removable cutting inserts attached to the body. The cutterhead body comprises a cylindrical portion having a plurality of circumferentially spaced grooves extending into the cutterhead body from the periphery thereof, which are adapted to receive the cutting inserts. A portion of the side walls of each groove is inwardly converging to substantially equally divide the forces exerted by the removable cutting insert between groove side walls, substantially reducing the circumferential spacing required between adjacent grooves.
Each of the cutting inserts used with the above cutterhead body includes a generally parallelepiped body having a blade aligned along its forward upper edge and a gullet portion aligned along its rear edge. Elongated slots in the body permit lateral adjustment along the axis of the cutterhead. The blade, which may be brazed on, mechanically fastened, or welded onto the insert body, has a generally L-shaped cross section, with an angular cutting edge for engaging the wood being cut, and a shoulder projecting below and in front of the blade to receive and assist in turning of chips in cooperation with the gullet of an adjacent cutting insert.
Individual cutting inserts in the above cutterhead can be replaced if broken or have otherwise reached the end of their useful life by exchanging the old cutting insert with a new cutting insert, thereby reducing the number of cutterheads required for a particular operation. The removed cutting insert can then be discarded or retipped with new cutting material. Alternately, worn inserts can be reground, either individually or in the assembled cutterhead. The new or reground inserts can be precisely installed and adjusted in the cutterhead body either on or off the machine.
While the foregoing cutterhead is a significant improvement over earlier cutterheads, further improvements are still desirable. For example, replacement of cutting inserts in the above-described cutterhead of U.S. Pat. No. 5,002,104 requires that the entire insert be replaced and the blade retipped. While this procedure is a substantial improvement over replacing solid, full-length cutterhead knives in the field, further convenience and savings are desirable. The current commercially feasible manner of attaching the blade to the cutting insert body, as shown in the U.S. Pat. No. 5,002,104 patent, is to braze or weld the blade onto the body, resulting in cutting blades that are difficult and expensive to refurbish, requiring extensive tool shop capabilities.
Therefore, it is a primary object of the present invention to provide an improved cutting insert having blades, which form the cutting edge, that can be quickly and economically replaced in the field. It is a further object of the invention to provide cutting inserts having blades that will withstand high impacts without damage due to elimination of brazing stresses. Another object of the invention is to provide a cutting insert structure permitting a wider use of cutting edge materials to meet various requirements. It is yet another object of the present invention to provide improved cutting inserts for cutterheads having these improvements.